Uniaxial tensile properties and constitutive model of high‐strength ECC reinforced with hybrid fibers

This study explored the mechanical properties and constitutive model of high‐strength engineered cementitious composites (HS‐ECC) reinforced with hybrid polyethylene (PE) and hooked‐end steel (ST) fibers. Three PE fiber volume contents (0.9%, 1.2%, and 1.5%) were selected, and varying amounts of ST fibers (0%–0.9%) were introduced to investigate the influence of fiber content and hybrid ratios on workability, compressive strength, and tensile properties. A nonlinear three‐stage tensile constitutive model was developed and validated. The results indicated that increasing fiber content reduced workability, with PE fibers having a stronger negative effect than ST fibers. In compression, ST fibers enhanced strength more significantly, while in tension, PE fibers improved strain capacity but slightly reduced tensile strength. ST fibers enhanced first crack strength and peak strength up to an optimal content, beyond which fiber clustering reduced tensile performance. Compared to PE‐only specimens, the addition of 0.3% ST fibers increased tensile strength by 1.35–1.75 times and peak strain by 1.78–3.59 times, with only a 4.9%–7.1% increase in material cost. Scanning electron microscopy confirmed that PE fibers contributed to multi‐crack control through interfacial slip and partial rupture, while ST fibers improved load transfer via mechanical anchorage and interfacial bonding. The proposed constitutive model accurately predicted the tensile stress–strain curves across fiber combinations. These findings provide quantitative guidance for optimizing the hybrid fiber design in HS‐ECC to balance workability, strength, ductility, and cost.